The present invention relates to a control apparatus for controlling the amount of grinding (by controlling the amount of feed) of a belt material in a grinding machine. For example, in the process of making belts, a vulcanized and molded cylindrical belt material (also referred to as slab) is ground on its outer or back side, prior to being cut into belts of a desired belt width, to finish the belt material thickness to a standard dimension.
A conventional apparatus of the following configuration has been normally used for controlling the amount of grinding when the belt material is ground to a specified thickness by a grinding machine.
As shown in FIG. 7, a base 2' on which a grinding machine 3' having a grinding belt 7' is mounted is slidably arranged on a head 12'. A driving motor 70 is mounted on one end of the base 2'. A ball screw rod or feed screw rod 72 connected to the driving shaft of the driving motor 70 by a coupling 71 is screwed into an internally threaded member 73 fixed onto the under surface of the head 12'. The screw rod 72 is turned to force the grinding machine 3' into contact with a belt material A mounted on a main shaft roll 21' held in a fixed position on the base 2' and a tension roll 26' to grind the belt material A by means of the revolving grinding belt 7'. When the amount of feed of the grinding belt 7' relative to the base 2' and the belt material A reaches a preset value, the driving motor 70 is stopped to terminate the grinding operation.
There is also a grinding amount control apparatus that uses a hydraulic cylinder in place of the driving motor and screw rod for moving the grinding machine, and a manually operated apparatus that uses no control apparatus for moving the grinding machine.
Of the above-mentioned conventional grinding amount control devices, in the case of the controlling apparatus using the driving motor 70 (FIG. 7), to raise the control accuracy, it is necessary to use an expensive driving motor 70 such as a servomotor or a pulse motor; thus the production cost increases. Moreover, when the so-called load control is made, wherein when the load resistance working on the grinding belt 7' increases during the grinding operation of a belt material A, the rotation of the driving motor 70 will be stopped for awhile to interrupt the feed of the grinding belt 7' towards the belt material A, the driving motor 70 tends to be affected by disturbances such as noise, possibly making the load control unreliable.
In the case of the control apparatus using a hydraulic cylinder as the apparatus for moving the grinding machine, the control tends to be unstable since a change in the oil temperature is accompanied with a change in the accuracy of control of the grinding amount. Moreover, because of the nature of the mechanism, delicate control of the grinding amount by means of a hydraulic cylinder is difficult.
In the case of the control apparatus by manual operation, an operator must attend the apparatus throughout its operation. Hence its working efficiency is very low and the workload of the operator is excessive.